コード例 #1
0
ファイル: XYZTrajectory.py プロジェクト: PytLab/KMCLib
    def __init__(self,
                 trajectory_filename,
                 configuration,
                 max_buffer_size=None,
                 max_buffer_time=None):
        """
        Constructor for the XYZTrajectory.

        :param trajectory_filename: The file name to write trajectory information to.
        :type trajectory_filename: str

        :param sites: The lattice sites of the configuration as an Nx3 list.

        :param max_buffer_size: The max size of the the buffer in memory
                                before writing to file.
        :type max_buffer_size: int

        :param max_buffer_time: The max time limit between dumps to file.
        :type max_buffer_time: float
        """
        # Call the base class constructor.
        Trajectory.__init__(self,
                            trajectory_filename,
                            max_buffer_size,
                            max_buffer_time)

        # Init the member data.
        self.__atom_id_types = []
        self.__atom_id_coordinates = []
        self.__time = []
        self.__step = []

        # Write the header.
        self.__writeHeader(configuration)
コード例 #2
0
    def __init__(self,
                 trajectory_filename,
                 configuration,
                 max_buffer_size=None,
                 max_buffer_time=None):
        """
        Constructor for the Trajectory.

        :param trajectory_filename: The file name to write trajectory information to.
        :type trajectory_filename: str

        :param sites: The lattice sites of the configuration as an Nx3 list.

        :param max_buffer_size: The max size of the the buffer in memory
                                before writing to file.
        :type max_buffer_size: int

        :param max_buffer_time: The max time limit between dumps to file.
        :type max_buffer_time: float
        """
        # Call the base class constructor.
        Trajectory.__init__(self, trajectory_filename, max_buffer_size,
                            max_buffer_time)

        # Init the member data.
        self.__types_buffer = []
        self.__simulation_time_buffer = []
        self.__step_buffer = []

        # Write the header.
        self.__writeHeader(configuration.sites())
コード例 #3
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ファイル: TrajectoryTest.py プロジェクト: PytLab/KMCLib
    def testAppendAndFlushBufferSize(self):
        """ Test that the append function flushes when the buffer size is large. """
        # Setup data.
        simulation_time = 12.3
        step = 14
        class Config:
            def __init__(self):
                pass
        configuration = Config()

        # Instantiate a trajectory.
        t = Trajectory(trajectory_filename="filename")

        # Add the needed functions.
        def storeData(*args, **kwargs):
            pass
        t._storeData = storeData

        ret_buffer = 10.0
        def bufferSize(*args, **kwargs):
            return ret_buffer
        t._bufferSize = bufferSize

        class Dummy:
            self.fc = False

        d = Dummy()
        def flush():
            d.fc = True

        t.flush = flush

        # Append.
        t.append(simulation_time, step, configuration)

        # The first time allways flushes.
        self.assertTrue(d.fc)

        # Append again.
        d.fc = False
        t.append(simulation_time, step, configuration)
        self.assertFalse(d.fc)

        # Change the value of the buffer size so that flush() gets called.
        ret_buffer = t._Trajectory__max_buffer_size + 1

        # Append.
        t.append(simulation_time, step, configuration)

        # Check.
        self.assertTrue(d.fc)
コード例 #4
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ファイル: TrajectoryTest.py プロジェクト: zqhuang2014/KMCLib
    def testAppendInterface(self):
        """ Test that the append function can not be called directly from the baseclass. """
        # Setup data.
        simulation_time = 12.3
        step = 14

        class Config:
            def __init__(self):
                pass

        configuration = Config()

        # Instantiate a trajectory.
        t = Trajectory(trajectory_filename="filename")

        # Call append.
        self.assertRaises(
            AttributeError,
            lambda: t.append(simulation_time, step, configuration))

        # Add the missing function.
        def storeData(*args, **kwargs):
            pass

        t._storeData = storeData

        self.assertRaises(
            AttributeError,
            lambda: t.append(simulation_time, step, configuration))

        # Add the missing function.
        def bufferSize(*args, **kwargs):
            pass

        t._bufferSize = bufferSize

        self.assertRaises(
            AttributeError,
            lambda: t.append(simulation_time, step, configuration))

        # Add the missing function.
        def flush(*args, **kwargs):
            pass

        t.flush = flush

        # Now it works.
        t.append(simulation_time, step, configuration)
コード例 #5
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ファイル: TrajectoryTest.py プロジェクト: zqhuang2014/KMCLib
    def testDefaultConstruction(self):
        """ Test default construction. """
        t = Trajectory(trajectory_filename="filename")

        # Check the member data.
        self.assertEqual(t._trajectory_filename, "filename")
        self.assertEqual(t._Trajectory__max_buffer_size, 10485760)  # 10 MB
        self.assertEqual(t._Trajectory__max_buffer_time, 1800.0)  # 30 min
コード例 #6
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ファイル: TrajectoryTest.py プロジェクト: zqhuang2014/KMCLib
 def testConstruction(self):
     """ Test that we can instantiate the Trajectory base class. """
     t = Trajectory(trajectory_filename="filename",
                    max_buffer_size=100,
                    max_buffer_time=30.0)
     # Check the member data.
     self.assertEqual(t._trajectory_filename, "filename")
     self.assertEqual(t._Trajectory__max_buffer_size, 100)
     self.assertEqual(t._Trajectory__max_buffer_time, 30.0)
コード例 #7
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ファイル: TrajectoryTest.py プロジェクト: PytLab/KMCLib
    def testAppendInterface(self):
        """ Test that the append function can not be called directly from the baseclass. """
        # Setup data.
        simulation_time = 12.3
        step = 14
        class Config:
            def __init__(self):
                pass
        configuration = Config()

        # Instantiate a trajectory.
        t = Trajectory(trajectory_filename="filename")

        # Call append.
        self.assertRaises(AttributeError,
                          lambda: t.append(simulation_time, step, configuration))

        # Add the missing function.
        def storeData(*args, **kwargs):
            pass
        t._storeData = storeData

        self.assertRaises(AttributeError,
                          lambda: t.append(simulation_time, step, configuration))

        # Add the missing function.
        def bufferSize(*args, **kwargs):
            pass
        t._bufferSize = bufferSize

        self.assertRaises(AttributeError,
                          lambda: t.append(simulation_time, step, configuration))

        # Add the missing function.
        def flush(*args, **kwargs):
            pass
        t.flush = flush

        # Now it works.
        t.append(simulation_time, step, configuration)
コード例 #8
0
ファイル: TrajectoryTest.py プロジェクト: PytLab/KMCLib
    def testAppendTimeUpdate(self):
        """ Test that the append function updates the time only when it flushes. """
        # Setup data.
        simulation_time = 12.3
        step = 14
        class Config:
            def __init__(self):
                pass
        configuration = Config()

        # Instantiate a trajectory.
        t = Trajectory(trajectory_filename="filename")

        # Add the needed functions.
        def storeData(*args, **kwargs):
            pass
        t._storeData = storeData

        ret_buffer = 10.0
        def bufferSize(*args, **kwargs):
            return ret_buffer
        t._bufferSize = bufferSize

        class Dummy:
            self.fc = False

        d = Dummy()
        def flush():
            d.fc = True

        t.flush = flush

        # Append.
        t.append(simulation_time, step, configuration)

        # The first time allways flushes.
        self.assertTrue(d.fc)

        # This updates the time last dump variable.
        ref_time_last_dump = t._Trajectory__time_last_dump

        # Sleep 10 ms.
        time.sleep(0.01)

        # Append again.
        d.fc = False
        t.append(simulation_time, step, configuration)
        self.assertFalse(d.fc)

        # This does not update the time last dump.
        self.assertAlmostEqual(ref_time_last_dump,  t._Trajectory__time_last_dump, 10)

        # Change the value of the max buffer time so that flush() gets called.
        t._Trajectory__max_buffer_time = 0.0

        # Sleep 10 ms.
        time.sleep(0.01)

        # Append.
        t.append(simulation_time, step, configuration)

        # Check.
        self.assertTrue(d.fc)

        # The time last dump should have been updated.
        self.assertTrue( (t._Trajectory__time_last_dump - ref_time_last_dump) > 0.0001 )
コード例 #9
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ファイル: KMCLatticeModel.py プロジェクト: lulzzz/KMCLib
    def run(self,
            control_parameters=None,
            trajectory_filename=None):
        """
        Run the KMC lattice model simulation with specified parameters.

        :param control_paramters:   An instance of KMCControlParameters specifying
                                    number of steps to run etc.

        :param trajectory_filename: The filename of the trajectory. If not given
                                    no trajectory will be saved.
        """
        # Check the input.
        if not isinstance(control_parameters, KMCControlParameters):
            msg ="""
The 'control_parameters' input to the KMCLatticeModel run funtion
must be an instance of type KMCControlParameters."""
            raise Error(msg)

        # Check the trajectory filename.
        use_trajectory = True
        if trajectory_filename is None:
            use_trajectory = False
            msg =""" KMCLib: WARNING: No trajectory filename given -> no trajectory will be saved."""
            prettyPrint(msg)

        elif not isinstance(trajectory_filename, str):
            msg = """
The 'trajectory_filename' input to the KMCLattice model run function
must be given as string."""
            raise Error(msg)

        # Construct the C++ lattice model.
        prettyPrint(" KMCLib: setting up the backend C++ object.")
        cpp_model = self._backend()

        # Print the initial matching information if above the verbosity threshold.
        if self.__verbosity_level > 9:
            self._printMatchInfo(cpp_model)

        # Check that we have at least one available process to  run the KMC simulation.
        if cpp_model.interactions().totalAvailableSites() == 0:
            raise Error("No available processes. None of the processes you have defined as input match any position in the configuration. Change your initial configuration or processes to run KMC.")

        # Setup a trajectory object.
        if use_trajectory:
            trajectory = Trajectory(trajectory_filename=trajectory_filename,
                                    sites=self.__configuration.sites())
            # Add the first step.
            trajectory.append(simulation_time  = self.__cpp_timer.simulationTime(),
                              step             = 0,
                              types            = self.__configuration.types())

        # Get the needed parameters.
        n_steps = control_parameters.numberOfSteps()
        n_dump  = control_parameters.dumpInterval()
        prettyPrint(" KMCLib: Runing for %i steps, starting from time: %f\n"%(n_steps,self.__cpp_timer.simulationTime()))

        # Run the KMC simulation.
        try:
            # Loop over the steps.
            for s in range(n_steps):
                step = s+1

                # Check if it is possible to take a step.
                nP = cpp_model.interactions().totalAvailableSites()
                if nP == 0:
                    raise Error("No more available processes.")

                # Take a step.
                cpp_model.singleStep()

                if ((step)%n_dump == 0):
                    prettyPrint(" KMCLib: %i steps executed. time: %f "%(step, self.__cpp_timer.simulationTime()))

                    # Perform IO using the trajectory object.
                    if use_trajectory:
                        trajectory.append(simulation_time  = self.__cpp_timer.simulationTime(),
                                          step             = step,
                                          types            = self.__configuration.types())
        finally:
            # Flush the buffers when done.
            if use_trajectory:
                trajectory.flush()
コード例 #10
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ファイル: TrajectoryTest.py プロジェクト: lulzzz/KMCLib
    def testFlush(self):
        """ Make sure we can flush the buffer as expected. """
        # Get a filename.
        name = os.path.abspath(os.path.dirname(__file__))
        name = os.path.join(name, "..", "..")
        name = os.path.join(name, "TestUtilities", "Scratch")
        trajectory_filename = os.path.join(name, "tmp_trajectory_file.py")
        self.__files_to_remove.append(trajectory_filename)

        # Construct the trajecctory object.
        sites = [[0.0,1.0,2.3],
                 [1.0,0.0,2.3],
                 [1.0,1.0,0.3],
                 [1.0,1.0,2.3],
                 [3.4,4.5,4.3],
                 [3.4,4.3,4.3],
                 [3.4,5.5,4.3],
                 [3.7,7.5,6.5]]

        # Construct.
        t = Trajectory(trajectory_filename, sites)

        # Check that the file is created but only with meta information.
        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        empty_list = []

        ret_types = local_dict['types']
        self.assertEqual( ret_types, empty_list )

        ret_times = local_dict['times']
        self.assertEqual( ret_times, empty_list )

        ret_steps = local_dict['steps']
        self.assertEqual( ret_steps, empty_list )

        # Fill the buffers.
        t._Trajectory__types_buffer           = [["ABC", "123"],["123", "ABC"]]
        t._Trajectory__simulation_time_buffer = [1.234, 5.678]
        t._Trajectory__step_buffer = [1, 99]

        # Flush the buffers.
        t.flush()

        # Check that the buffers are empty.
        self.assertEqual( t._Trajectory__types_buffer, empty_list )
        self.assertEqual( t._Trajectory__simulation_time_buffer, empty_list )
        self.assertEqual( t._Trajectory__step_buffer, empty_list )

        # Check that the file has the flushed values.
        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        ret_types = local_dict['types']
        self.assertEqual( ret_types, [["ABC", "123"],["123", "ABC"]] )

        ret_times = local_dict['times']
        self.assertAlmostEqual( ret_times, [1.234, 5.678], 10 )

        ret_steps = local_dict['steps']
        self.assertEqual( ret_steps, [1, 99] )
コード例 #11
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ファイル: TrajectoryTest.py プロジェクト: lulzzz/KMCLib
    def testAppend(self):
        """ Test appending to the trajectory. """
        # Setup input.
        sites = [[0.0,1.0,2.3],
                 [1.0,0.0,2.3],
                 [1.0,1.0,0.3],
                 [1.0,1.0,2.3],
                 [3.4,4.5,4.3],
                 [3.4,4.3,4.3],
                 [3.4,5.5,4.3],
                 [3.7,7.5,6.5]]
        name = os.path.abspath(os.path.dirname(__file__))
        name = os.path.join(name, "..", "..")
        name = os.path.join(name, "TestUtilities", "Scratch")
        trajectory_filename = os.path.join(name, "tmp_trajectory_file.py")
        self.__files_to_remove.append(trajectory_filename)

        # Construct.
        t = Trajectory(trajectory_filename, sites)

        # Append times, steps and typers.
        t.append(1.10045, 12,
                 ["A", "A", "A", "A", "A", "A"] )

        # Since this was the first time it should have triggered a dump to file.
        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        # Needed to prevent test failure.
        MPICommons.barrier()

        # Check the types.
        ret_types = local_dict['types']
        ref_types = [["A", "A", "A", "A", "A", "A"]]
        self.assertEqual( ret_types, ref_types )

        # Check the steps.
        ret_steps = local_dict['steps']
        ref_steps = [12]
        self.assertEqual( ret_steps, ref_steps )

        # Check the times.
        ret_times = local_dict['times']
        ref_times = [1.10045]
        self.assertEqual( ret_times, ref_times )

        # Appending again directly makes no dump.
        t.append(1.1993, 14,
                 ["B", "B", "B", "B", "B", "B"] )

        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        # Needed to prevent test failure.
        MPICommons.barrier()

        # Check.
        ret_types = local_dict['types']
        self.assertEqual( ret_types, ref_types )
        ret_steps = local_dict['steps']
        self.assertEqual( ret_steps, ref_steps )
        ret_times = local_dict['times']
        self.assertEqual( ret_times, ref_times )

        # But if we dump again and set the time limit to zero we will trigger a dump.
        t._Trajectory__max_buffer_time = 0.0
        t.append(1.199, 19,
                 ["C", "C", "C", "C", "C", "C"] )

        # Reset the time to some thing large.
        t._Trajectory__max_buffer_time = 100000000000.0

        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        # Check the types.
        ret_types = local_dict['types']
        ref_types = [["A","A","A","A","A","A"],
                     ["B","B","B","B","B","B"],
                     ["C","C","C","C","C","C"]]

        # Needed to prevent test failure.
        MPICommons.barrier()

        self.assertEqual( ret_types, ref_types )

        # Check the steps.
        ret_steps = local_dict['steps']
        ref_steps = [12,14,19]
        self.assertEqual( ret_steps, ref_steps )

        # Check the times.
        ret_times = local_dict['times']
        ref_times = [1.10045, 1.1993, 1.199]
        self.assertEqual( ret_times, ref_times )

        # The buffers are reset after each dump. If we make the
        # max size limit smaller than the size of the appended types
        # list this must trigger a dump.
        types = ["A","A","A","A","A","B"]
        size = sys.getsizeof(types)
        t._Trajectory__max_buffer_size = size

        # Append.
        t.append(1.1995, 43, types )

        # Check.
        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        ret_types = local_dict['types']
        ref_types = [["A","A","A","A","A","A"],
                     ["B","B","B","B","B","B"],
                     ["C","C","C","C","C","C"]]

        # Needed to prevent test failure.
        MPICommons.barrier()

        self.assertEqual( ret_types, ref_types )

        # Append.
        t.append(1.1995, 43, types )
        t.append(1.1995, 43, types )
        t.append(1.1995, 43, types )
        # This last one triggers the dump.
        t.append(1.1995, 43, types )

        # Check.
        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        ret_types = local_dict['types']
        ref_types = [["A","A","A","A","A","A"],
                     ["B","B","B","B","B","B"],
                     ["C","C","C","C","C","C"],
                     ["A","A","A","A","A","B"],
                     ["A","A","A","A","A","B"],
                     ["A","A","A","A","A","B"],
                     ["A","A","A","A","A","B"],
                     ["A","A","A","A","A","B"]]

        # Needed to prevent test failure.
        MPICommons.barrier()

        self.assertEqual( ret_types, ref_types )
コード例 #12
0
ファイル: TrajectoryTest.py プロジェクト: lulzzz/KMCLib
    def testWriteToFile(self):
        """ Test writing the buffers to file. """
        # Setup input.
        sites = [[0.0,1.0,2.3],
                 [1.0,0.0,2.3],
                 [1.0,1.0,0.3],
                 [1.0,1.0,2.3],
                 [3.4,4.5,4.3],
                 [3.4,4.3,4.3],
                 [3.4,5.5,4.3],
                 [3.7,7.5,6.5]]
        name = os.path.abspath(os.path.dirname(__file__))
        name = os.path.join(name, "..", "..")
        name = os.path.join(name, "TestUtilities", "Scratch")
        trajectory_filename = os.path.join(name, "tmp_trajectory_file.py")
        self.__files_to_remove.append(trajectory_filename)

        # Construct.
        t = Trajectory(trajectory_filename, sites)

        # Write times, steps and typers.
        times = [1.10045, 2.334156, 3.4516410]
        steps = [12, 25, 52]
        types = [["ThisIsTheLongestTypeNameIHaveEverEncounteredPerhaps",
                  "here", "is", "Next", "Long", "List", "Offffffff", "Names", "now", "this", "one", "is", "longer", "still"],
                 ["A", "B", "C", "D", "E", "F", "G", "H"],
                 ["1", "2", "4", "5", "6", "5" ,"43", "243r2424"]]

        # Needed to prevent test failure.
        MPICommons.barrier()

        # Check that the time is zero before we start.
        self.assertAlmostEqual( t._Trajectory__time_last_dump, 0.0, 10 )

        t._Trajectory__writeToFile(times, steps, types)

        # Needed to prevent test failure.
        MPICommons.barrier()

        # Check that the time stamp was updated.
        self.assertTrue( 1357651850 < t._Trajectory__time_last_dump )
        last_time = t._Trajectory__time_last_dump

        # Check the info stored in the file.
        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        # Check the types.
        ret_types = local_dict['types']
        ref_types = [['ThisIsTheLongestTypeNameIHaveEverEncounteredPerhaps',
                      'here', 'is', 'Next', 'Long', 'List', 'Offffffff',
                      'Names', 'now', 'this', 'one', 'is', 'longer', 'still'],
                     ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'],
                     ['1', '2', '4', '5', '6', '5', '43', '243r2424']]

        # Needed to prevent test failure.
        MPICommons.barrier()

        self.assertEqual( ret_types, ref_types )

        # Check the steps.
        ret_steps = local_dict['steps']
        ref_steps = [12, 25, 52]
        self.assertEqual( ret_steps, ref_steps )

        # Check the times.
        ret_times = local_dict['times']
        ref_times = [1.10045, 2.334156, 3.451641]
        self.assertEqual( ret_times, ref_times )

        # Sleep for two seconds before we add again.
        time.sleep(1)
        t._Trajectory__writeToFile(times, steps, types)

        # Check the time.
        self.assertTrue( (t._Trajectory__time_last_dump - last_time > 1) )

        # Now, check the file again.
        global_dict = {}
        local_dict  = {}
        execfile(trajectory_filename, global_dict, local_dict)

        # Check the types.
        ret_types = local_dict['types']
        ref_types = [['ThisIsTheLongestTypeNameIHaveEverEncounteredPerhaps',
                      'here', 'is', 'Next', 'Long', 'List', 'Offffffff',
                      'Names', 'now', 'this', 'one', 'is', 'longer', 'still'],
                     ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'],
                     ['1', '2', '4', '5', '6', '5', '43', '243r2424'],
                     ['ThisIsTheLongestTypeNameIHaveEverEncounteredPerhaps',
                      'here', 'is', 'Next', 'Long', 'List', 'Offffffff',
                      'Names', 'now', 'this', 'one', 'is', 'longer', 'still'],
                     ['A', 'B', 'C', 'D', 'E', 'F', 'G', 'H'],
                     ['1', '2', '4', '5', '6', '5', '43', '243r2424']]

        # Needed to prevent test failure.
        MPICommons.barrier()

        self.assertEqual( ret_types, ref_types )

        # Check the steps.
        ret_steps = local_dict['steps']
        ref_steps = [12, 25, 52, 12, 25, 52]
        self.assertEqual( ret_steps, ref_steps )

        # Check the times.
        ret_times = local_dict['times']
        ref_times = [1.10045, 2.334156, 3.451641, 1.10045, 2.334156, 3.451641]
        self.assertEqual( ret_times, ref_times )
コード例 #13
0
ファイル: TrajectoryTest.py プロジェクト: zqhuang2014/KMCLib
    def testAppendAndFlushBufferSize(self):
        """ Test that the append function flushes when the buffer size is large. """
        # Setup data.
        simulation_time = 12.3
        step = 14

        class Config:
            def __init__(self):
                pass

        configuration = Config()

        # Instantiate a trajectory.
        t = Trajectory(trajectory_filename="filename")

        # Add the needed functions.
        def storeData(*args, **kwargs):
            pass

        t._storeData = storeData

        ret_buffer = 10.0

        def bufferSize(*args, **kwargs):
            return ret_buffer

        t._bufferSize = bufferSize

        class Dummy:
            self.fc = False

        d = Dummy()

        def flush():
            d.fc = True

        t.flush = flush

        # Append.
        t.append(simulation_time, step, configuration)

        # The first time allways flushes.
        self.assertTrue(d.fc)

        # Append again.
        d.fc = False
        t.append(simulation_time, step, configuration)
        self.assertFalse(d.fc)

        # Change the value of the buffer size so that flush() gets called.
        ret_buffer = t._Trajectory__max_buffer_size + 1

        # Append.
        t.append(simulation_time, step, configuration)

        # Check.
        self.assertTrue(d.fc)
コード例 #14
0
ファイル: TrajectoryTest.py プロジェクト: zqhuang2014/KMCLib
    def testAppendTimeUpdate(self):
        """ Test that the append function updates the time only when it flushes. """
        # Setup data.
        simulation_time = 12.3
        step = 14

        class Config:
            def __init__(self):
                pass

        configuration = Config()

        # Instantiate a trajectory.
        t = Trajectory(trajectory_filename="filename")

        # Add the needed functions.
        def storeData(*args, **kwargs):
            pass

        t._storeData = storeData

        ret_buffer = 10.0

        def bufferSize(*args, **kwargs):
            return ret_buffer

        t._bufferSize = bufferSize

        class Dummy:
            self.fc = False

        d = Dummy()

        def flush():
            d.fc = True

        t.flush = flush

        # Append.
        t.append(simulation_time, step, configuration)

        # The first time allways flushes.
        self.assertTrue(d.fc)

        # This updates the time last dump variable.
        ref_time_last_dump = t._Trajectory__time_last_dump

        # Sleep 10 ms.
        time.sleep(0.01)

        # Append again.
        d.fc = False
        t.append(simulation_time, step, configuration)
        self.assertFalse(d.fc)

        # This does not update the time last dump.
        self.assertAlmostEqual(ref_time_last_dump,
                               t._Trajectory__time_last_dump, 10)

        # Change the value of the max buffer time so that flush() gets called.
        t._Trajectory__max_buffer_time = 0.0

        # Sleep 10 ms.
        time.sleep(0.01)

        # Append.
        t.append(simulation_time, step, configuration)

        # Check.
        self.assertTrue(d.fc)

        # The time last dump should have been updated.
        self.assertTrue(
            (t._Trajectory__time_last_dump - ref_time_last_dump) > 0.0001)